Friction Clutch For Accessory Drive

ABSTRACT

A fail-safe friction clutch assembly for a vehicle accessory, particularly to drive a vehicle cooling pump or cooling fan. The friction clutch assembly includes a friction plate member connected to a central rotatable shaft member used for operating the vehicle accessory. A pair of friction lining members arc positioned on opposite sides of the friction plate member. An armature member is spring biased to axially force the friction plate member and friction lining member against a housing or cover which is rotating at input speed. A solenoid assembly is used to overcome the spring bias and pull the armature and friction plate member away from the housing.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. patent applicationSer. No. 14/135,280 (DKT12180A (BWA 0427 PUS) filed on Dec. 19, 2013,which is a non-provisional of U.S. patent application Ser. No.61/745,647, filed on Dec. 24, 2012. This application is also related toU.S. patent application Ser. No. 61/474,862 and U.S. patent applicationSer. No. 61/474,928, both filed on Apr. 13, 2011.

TECHNICAL FIELD

Friction clutch drive assemblies, particularly for vehicle accessoriessuch as coolant pumps, are disclosed.

BACKGROUND

Accessories such as water pumps and cooling fans are in common use invehicles such as automobiles and trucks with internal combustionengines. The accessories are typically driven by a belt directly orindirectly attached to the crankshaft of the engine and thus operate atsome percentage of engine speed. The water pumps have an impeller thatis used to circulate the engine coolant from the engine to the radiatorand back in order to keep the coolant within acceptable temperaturelimits. Cooling fans have a fan with blades that supplies atmosphere airto a radiator, for example, to cool the engine coolant.

Efforts are being made today to reduce the power consumption of engineaccessories, such as water pumps and fan drives, in order to improvefuel economy and reduce emissions. It would thus be preferable if suchaccessories could be made to operate with less power, or only whenneeded, in order to reduce the load on the engine and, in turn, improvefuel economy and reduce undesirable emissions from the engine.

SUMMARY OF THE INVENTION

A vehicle accessory drive assembly, such as a cooler pump or fan drive,having an improved dry friction clutch mechanism is disclosed. Theaccessory can have an ON-OFF operation with an electromagneticallyoperated friction clutch which can selectively rotate a shaft member.The components for the operation are included as part of amulti-component assembly that includes a pulley member. The pulley isturned at input speed by an engine belt positioned on the pulley member.In use as a water pump, a shaft connected to the impeller of the waterpump is positioned in the assembly and is controlled in an ON-OFF mannerby a friction clutch mechanism. Similarly, in use as a fan drive, theoperation of the accessory drive is controlled as an ON-OFF manner by afriction clutch mechanism.

The friction clutch assembly is positioned inside the assembly toselectively allow operation mechanically by the pulley member. The dryfriction clutch assembly is activated by turning on/off a solenoid. Whenthe solenoid is off (i.e. not energized), the clutch will be engaged,and thus the clutch is fail-safe. A number of springs push an armatureplate which clamps a friction plate between the armature plate and acover member. Torque is transferred through both sides of the frictionplate. The clutch is disengaged by turning on the solenoid.

When the solenoid is on (i.e. energized), the solenoid force overcomesthe force of the springs and pulls the armature plate back against thepulley. A return spring pushes the friction plate away from the coverand holds it against a stop, creating air gaps on both sides of thefriction plate. In this state of operation, the input (pulley) andoutput (shaft) are disconnected, eliminating interaction (e.g. bearingdrag) between the input and output.

Further objects, features and benefits of the invention are set forthbelow in the following description of the invention when viewed incombination with the drawings and appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a vehicle water pump assembly inaccordance with an embodiment of the invention.

FIG. 2 is an exploded view of the assembly of FIG. 1.

FIG. 2A is an exploded view of a portion of the assembly of FIG. 1.

FIG. 3 is a cross-sectional view of the assembly shown in FIGS. 1 and 2with the components shown in the solenoid disengaged position.

FIG. 4 is a cross-sectional view of the assembly shown in FIGS. 1 and 2with the components shown in the solenoid engaged position.

FIG. 5 is a cross-sectional view of a vehicle cooling fan assembly inaccordance with another embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

For the purpose of promoting and understanding the principles of thepresent invention, reference will now be made to the embodimentsillustrated in the drawings and specific language will be used todescribe them. It will nevertheless be understood that no limitation asto the scope of the invention is hereby intended. The invention includesany alternatives and other modifications in the illustrated devices anddescribed methods and further applications of the principles of theinvention which would normally occur to persons or ordinary skill in theart to which the invention relates.

The present inventions described herein particularly relate to frictionclutch assemblies particularly used for coolant pumps and cooling fans.The coolant pumps circulate the coolant in an engine, such as anautomobile internal combustion engine. (The terms “water pump” and“coolant pump” are used interchangeably herein.) The cooling fans areused to push or pull air through a radiator to help reduce thetemperature of the engine coolant.

The preferred embodiments of the present invention as described hereinare particularly adapted for use with trucks, passenger cars andoff-highway vehicles.

An accessory assembly embodiment used to operate a cooling pump is shownin FIGS. 1-4. It is generally referred to by the reference numeral 200.The assembly includes a housing 202 and an impeller 204 which is used tocirculate the engine cooling fluid in the vehicle.

The housing 202 includes a base member 206 and a cover member 208, whichcan be secured together by a plurality of fasteners, such as bolts 210.A solenoid actuated friction clutch mechanism 212 is positioned in thehousing. A central shaft member 214 is positioned centrally in thehousing and is used to rotate the impeller 204. The impeller ispositioned in a housing (not shown) and is connected to the shaft member214 by a fitting assembly 216. The lower end 214L of the shaft issecured to the assembly 216 in any conventional manner.

The assembled housing includes a pulley member 220. The pulley member isadapted to be driven by an engine belt, either directly or indirectly bythe engine crankshaft. Although the outside surface 223 of the pulleymember is smooth in the drawings, it can have any conventional shape inorder to mesh or mate with the engine belt.

The shaft member 214 is rotatably supported in the housing 202 bybearing set member 230. Although only one bearing set 230 is shown, morethan one sets of bearings or stacked bearings can be utilized.

The friction clutch mechanism 212 includes an armature plate 232, afriction plate 234 and two annular rings of friction material 236, 238.The armature plate 232 is preferably made of a magnetic metal material,such as low carbon steel. The friction plate 234 is preferably made of anon-magnetic material, such as stainless steel.

The friction material 236, 238 can be any conventional frictionmaterials used in friction clutches today, and can be complete rings,segments of rings, or simply pieces of friction material positionedgenerally where rings 236, 238 are shown in the drawings. The frictionmaterials are fixedly attached to the two sides of the friction plateby, for example, bonding using a bonding agent.

The cover member 208 which preferably is made of a non-magneticmaterial, such as stainless steel, is connected directly to the pulleymember 220 by the connecting pin members, such as fasteners or bolts210. The ends of the fasteners can be threaded for mating withcorresponding mating threads in openings 221 in the pulley member 220.Thus, when the pulley is rotated by an engine belt (not shown); thecover member 208 rotates at the same input speed.

The pulley member 220 is preferably made of a magnetic metal material,such as low carbon steel. The pulley member rotates freely aroundbearings 240. Although the bearings can be of any type that will havesufficient durability and performance, a pair of stacked bearings 240can be utilized, as shown in the drawings.

The operation of the friction clutch assembly is performed by a solenoidassembly 250. The solenoid assembly includes a solenoid coil 252 whichis positioned in the base member 206 of the housing 202. The solenoidcoil member comprises a donut-shaped coil of copper wires, while thesolenoid housing is preferably made of a magnetic material, such as lowcarbon steel. The solenoid coil member 252 is preferably potted in thehousing member 206.

A nut member 260 is threaded, or otherwise firmly fixed, on the end ofthe shaft member 214. The friction plate member 234 is connected, suchas being keyed, to the nut member 260. As shown in FIG. 2, the nutmember has a plurality of spline members 261 which fit withincorresponding notches 235 in the center of the friction plate member234. In this manner, the nut and friction plate members rotate with theshaft member 214. The nut member 260 and the shaft member 214 firmlyclamp a stop member 270 and the bearing member 230 together. The shaftmember 214 and all components fixed on it are positioned axially by thebearing member 230. The stop member 270 is preferably made of anon-metallic material, such as stainless steel.

To fix the bearing member 230 in an axial position inside the housing206, a wave spring member 280 and bearing retainer member 282 areutilized. The bearing retainer member 282 is threadedly affixed to thehousing 206 as shown by reference number 284.

The stop member 270 is utilized to stop the axial movement of thefriction plate member 234 when the solenoid assembly 250 is energized,as explained below. A return spring 290 is positioned between the nutmember 260 and the friction plate member 234 and acts to return thefriction plate member 234 to its mechanical disengaged position when thesolenoid assembly 250 is actuated.

The solenoid coil 252 is electrically powered through a circuit board(not shown). Electrical leads and wires can be insert molded in thehousing 206 in order to carry the electrical signals to the solenoidcoil member 252. The circuit board further communicates with theelectronic control unit (ECU) of the vehicle through the vehiclecommunication network such as a CAN network. The water pump assemblycontroller circuit board could also be positioned inside the housing206, possibly having a donut shape.

Activation of the water pump is selected according to the coolingrequired for the engine. Sensors feed relevant data to the ECU whichthen sends a signal to the pump controller requesting that the pump beactivated. The pump controller then engages the friction clutch whichallows the impeller to be driven by the pulley.

When activation of the water pump is not needed, the friction clutchassembly is held in a disengaged position by the solenoid assembly 250.This is shown in FIG. 4. When the solenoid coil member 252 iselectrically activated, a flux circuit 300 is created which acts to pullthe armature plate 232 toward the solenoid coil member overcoming theforce of the coil spring members 302. With the armature plate 232 pulledtoward the solenoid, the return spring 290 holds the friction plate 234against the stop member 270. In this condition, the friction materialson the friction plate 234 are not in contact with either the covermember 208 or the armature plate 232.

The number of coil springs 302 and their biasing force is determinedaccording to the force needed in the assembly. Six coil springs 302 areshown in the drawings, but there can be more or less than this amountdepending on the force needed.

In this deactivation mode of operation, there are air gaps on theexterior sides of the friction materials on the friction plate, and theinput (pulley member) and output (shaft member) are disconnected. Thiseliminates any interaction, such as bearing drag between the input andoutput.

In order to create an appropriate flux circuit 300, the pulley member220 has a plurality of openings 310 which create air gaps. This isparticularly shown in FIGS. 2A, as well as FIG. 4. The openings 310essentially form an annular open ring. With the air gaps, the pulleymember is, for electromagnetic purposes, essentially an outer annularring 312 and a separated annular inner ring 314. The size, shape andnumber of openings or slots 310 is not critical, so long as they fulfillthe purposes of creating a break in the magnetic flux.

The flux circuit 300 is shown in FIG. 4. It runs through the solenoidhousing 206, the belt engaging portion 223 of the pulley member 220,outer annular ring portion 312 of the pulley member, and then jumps tothe armature plate member 232 and then back to the inner annular ringportion 314 of the pulley member 220 where it returns to the solenoidhousing. This circuit pulls the armature member tightly against thepulley member such that the armature member rotates with the pulleymember and at the same speed. In this condition, the water pump impeller204 is not activated.

FIG. 3 depicts the situation where the solenoid assembly 250 is notactivated. This is the “fail safe” condition. This causes the water pumpto be driven by an engine belt and activated. In this situation, coilsprings 302 force the armature member 232 in a direction away from thepulley member and away from the solenoid assembly. This causes thearmature member 232 to contact the friction member 236 which in turnforces the friction member 238 to contact the inner surface 209 of thecover member 208. Since the armature member, pulley member and covermember are all fixed together, this causes the shaft member 214 andimpeller member 204 to rotate at the same speed.

A path of torque transfer which mechanically rotates the shaft member isshown by arrows 320 in FIG. 3. In the engaged clutch, the friction platemember 234 is clamped between the cover member 208 and armature member232 and torque is transferred through both sides of the friction plate.There also is a torque transfer path from the pulley member 220, throughthe fastener 210, the armature plate member 232, the friction platemember 234, the nut member 290 and to the shaft 214.

FIG. 5 schematically depicts the use of the inventive friction clutchfor operating a cooling fan. The cooling fan accessory mechanism isreferred to generally by the reference numeral 400.

The friction clutch mechanism 410 is substantially the same as thefriction clutch mechanism described above which is utilized toselectively rotate a water pump impeller. In this embodiment, thefriction clutch mechanism is utilized to rotate a cooling fan. Thecomponents which are the same are referred to by the same referencenumerals as set forth in the other Figures. The main differences arethat the shaft member 214′, when activated, rotates a cooling fanassembly 420. The fan assembly 420 includes a cooling fan 430 with anumber of blade members 440 and central hub member 450. The hub member450 is securely attached to the shaft member 214′, and the fan 430 issecurely attached to the hub member 450, such that the housing fan andblades will rotate when the shaft member rotates and at the same speed.Any conventional means or mechanisms can be utilized to attach thecomponents together so they all rotate together.

The present water pump and cooling fan devices are designed to be springengaged so the accessory device is powered in the event of a controlfailure such as a loss of electrical power. This is done to provide“Fail-Safe” functionality meaning that the device defaults to its “on”state when it is not powered. If the electrical system of the coolantpump were to fail, the solenoid would be de-energized allowing the coilsprings to force the friction clutch assembly to become engaged.Therefore the pump would operate in mechanical mode with the impellerdriven by the pulley member through the clutch assembly, thus preventingoverheating.

Although the invention has been described with respect to preferredembodiments, it is to be also understood that it is not to be so limitedsince changes and modifications can be made therein which are within thefull scope of this invention as detailed by the following claims.

What is claimed is:
 1. A friction clutch assembly for a vehicle engineaccessory, the accessory having a housing member, a pulley member forrotating the housing member, an internal shaft member which isselectively rotatable for operating the accessory, and a solenoidassembly, said friction clutch assembly comprising: an armature member,said armature member made of a magnetic material and capable of axialmovement in a housing when energized by a solenoid assembly; a frictionplate member positioned adjacent said armature member; a pair offriction lining members, each of said pair positioned on opposite sidesof said friction plate member; biasing members biasing said armaturemember in an axial direction away from the solenoid assembly; whereinwhen said solenoid assembly is actuated, said armature member is pulledaxially toward said solenoid member preventing either of said pair offriction lining members from contacting the housing member; and whereinwhen said solenoid assembly is not activated, said biasing members biassaid armature member axially against said friction plate member causingone of said pair of friction lining members to contact said housingmember causing rotation of said internal shaft member and operating saidaccessory.
 2. The friction clutch assembly as set forth in claim 1further comprising a water pump impeller attached to said shaft member,wherein said accessory is a water pump.
 3. The friction clutch assemblyas set forth in claim 1 further comprising a fan member attached to saidshaft member, wherein said accessory is a cooling fan.
 4. The frictionclutch assembly as set forth in claim 1 wherein said biasing memberscomprises a plurality of coil spring members.
 5. The friction clutchassembly as set forth in claim 1 wherein each of said friction liningmembers comprise annular rings of friction lining material.
 6. Thefriction clutch assembly as set forth in claim 1 wherein the solenoidmember comprises a solenoid housing and a solenoid coil member.
 7. Thefriction clutch assembly as set forth in claim 1 wherein the flux pathfor axially moving said armature member when the solenoid assembly isactivated comprises a path through said solenoid assembly, said pulleymember, said armature member, back to said pulley member and then backto said solenoid assembly.
 8. The friction clutch assembly as set forthin claim 1 further comprising a return spring member for biasing saidfriction plate member axially toward said solenoid assembly.
 9. Thefriction clutch assembly as set forth in claim 1 wherein said housingmember comprises a cover member.
 10. The friction clutch assembly as setforth in claim 1 wherein when said solenoid member is activated, saidpair of friction lining members are prevented from contacting saidarmature member.
 11. A friction clutch assembly for a vehicle coolantpump, said coolant pump having a central shaft member for rotating animpeller, said friction clutch assembly comprising: a solenoid assemblycomprising a solenoid housing and a solenoid coil member; a pulleymember rotatable at input speed; a housing member attached to saidpulley member and rotatable therewith; an axially moveable magneticarmature member; biasing members for biasing said armature memberaxially away from said solenoid assembly; friction plate memberconnected to said central shaft member and rotatable therewith; a firstfriction lining member positioned on a first surface of said frictionplate member and adjacent said armature member; and a second frictionlining member positioned on a second and opposite surface of saidfriction plate member and adjacent said housing member; wherein whensaid solenoid assembly is not electrically actuated, said biasingmembers force said armature member and said friction plate memberaxially in a direction toward said housing member wherein said secondfriction lining member contacts said housing cover member causing saidfriction plate member and said central shaft member to rotate at inputspeed.
 12. The friction clutch assembly as set forth in claim 11 whereinsaid biasing members comprise a plurality of coil spring members. 13.The friction clutch assembly as set forth in claim 11 wherein said firstand second friction lining members each comprise annular rings offriction lining material.
 14. The friction clutch assembly as set forthin claim 11 wherein the flux path for axially moving said armaturemember when the solenoid assembly is activated comprises a path throughsaid solenoid assembly, said pulley member, said armature member, backto said pulley member and then back to said solenoid assembly.
 15. Thefriction clutch assembly as set forth in claim 11 further comprising areturn spring member for biasing said friction plate member axially awayfrom said housing cover member.
 16. The friction clutch assembly as setforth in claim 11 wherein said pulley member comprises a plurality ofopenings forming an insulating air gap and magnetic flux break betweenan inner ring portion and an outer ring portion.
 17. The friction clutchassembly as set forth in claim 11 wherein said pulley member and saidhousing cover member are attached together by a plurality of fastenermembers.
 18. The friction clutch assembly as set forth in claim 11wherein the connection between said friction plate member and saidcentral shaft member comprises a nut member.
 19. The friction clutchassembly as set forth in claim 11 wherein said solenoid assembly is notelectrically actuated, said armature member is forced against said firstfriction lining member, causing said armature member to rotate at inputspeed.
 20. The friction clutch assembly as set forth in claim 11 whereinsaid housing member comprises a cover member.
 21. A friction clutchassembly for a vehicle engine cooling fan, said cooling fan having acentral shaft member for rotating fan member, said friction clutchassembly comprising: a solenoid assembly comprising a solenoid housingand a solenoid coil member; a pulley member rotatable at input speed; ahousing member attached to said pulley member and rotatable therewith;an axially moveable magnetic armature member; biasing members forbiasing said armature member axially away from said solenoid assembly;friction plate member connected to said central shaft member androtatable therewith; a first friction lining member positioned on afirst surface of said friction plate member and adjacent said armaturemember; and a second friction lining member positioned on a second andopposite surface of said friction plate member and adjacent said housingmember; wherein when said solenoid assembly is not electricallyactuated, said biasing members force said armature member and saidfriction plate member axially in a direction toward said housing memberwherein said second friction lining member contacts said housing covermember causing said friction plate member and said central shaft memberto rotate at input speed.
 22. The friction clutch assembly as set forthin claim 21 wherein said biasing members comprise a plurality of coilspring members.
 23. The friction clutch assembly as set forth in claim21 wherein said first and second friction lining members each compriseannular rings of friction lining material.
 24. The friction clutchassembly as set forth in claim 21 wherein the flux path for axiallymoving said armature member when the solenoid assembly is activatedcomprises a path through said solenoid assembly, said pulley member,said armature member, back to said pulley member and then back to saidsolenoid assembly.
 25. The friction clutch assembly as set forth inclaim 21 further comprising a return spring member for biasing saidfriction plate member axially away from said housing cover member. 26.The friction clutch assembly as set forth in claim 21 wherein saidpulley member comprises a plurality of openings forming an insulatingair gap and magnetic flux break between an inner ring portion and anouter ring portion.
 27. The friction clutch assembly as set forth inclaim 21 wherein said solenoid assembly is not electrically actuated,said armature member is forced against said first friction liningmember, causing said armature member to rotate at input speed.
 28. Thefriction clutch assembly as set forth in claim 21 wherein said fanmember comprises a central hub member and a plurality of fan blademembers.